This invention relates to a device for voice communication with a person at a remote location, such as a TV conference system, TV phone through a cellular phone, and handsfree communication through a car navigation device, and a method thereof.
There is a telephone conference system or a TV conference system in which both a first location and a second location have a speaker and a microphone, and the first and second locations are connected to each other via a network in order to talk to persons at the remote location by means of voice. This system has a problem that a voice of a person closer to a place at which the microphone is installed is received at high level, and a voice of a person farther from the place at which the microphone is installed is received at low level.
In order to address this problem, a remote controller for volume control, with which a user can amplify volume by holding down a button for volume amplification, has conventionally been used.
However, the remote controller for volume control requires a manual adjustment of the volume each time the volume of speakers changes, resulting in a problem of a complicated manipulation.
To address this problem, an AGC for correcting speaker volume automatically has been used (refer to E. Hansler, G. Schmidt, “Acoustic Echo and Noise Control”, Wiley Series, pp. 148-151, 2004, and Japanese Patent Application Laid-open No. Hei 11-187130, for example).
However, the AGC has a problem that, when the volume of a speaker changes upon a change of the speaker, or the like, a period of time is required to adapt to volume after the change, and, during this period, a voice cannot be heard at a proper volume level. Moreover, when a background noise exists, the AGC may incorrectly recognize the background noise as a voice, and may incorrectly amplify the background noise, and it is thus difficult to use the AGC for a TV conference system when a background noise such as a sound of a fan for a projector exists.
There is proposed a method for adjusting an utterance level according to a position of a speaker in order to correct a volume level which is temporarily deviating from a proper level upon a change of the speaker (refer to Japanese Patent Applications Laid-open No. Hei 06-253305 and No. 2005-136701, for example). In those level adjusting methods, a position of utterance is identified according to some method, and, when an utterance position changes, according to a result of the identification, the change in utterance position is recognized. Then, a volume level corresponding to the utterance position is read from a memory, and the volume level is set to the level read from the memory. Moreover, the predicted utterance level is stored in a memory area according to the identified position of utterance. With those steps, the utterance level is adjusted upon a change of the speaker.